Method and system for transmitting/receiving data in a communication system

Abstract

A method and system for transmitting and receiving data to prevent Adjacent Channel Interference (ACI) in a Cognitive Radio (CR) communication system are provided, in which a second system using a second frequency band measures a first channel interference that a first frequency band used by a first system causes to the second frequency band, determines a frequency spreading parameter according to the first channel interference, measures a second channel interference that the second frequency band causes to the first frequency band, receives link information from the first system according to the second channel interference, determines a power allocation map according to the link information and transmits and receives data according to the frequency spreading parameter and the power allocation map.

1 . A method for transmitting and receiving data in a communication system having a first system for providing a communication service in a first frequency band and a second system for providing a communication service in a second frequency band different from the first frequency band, the method comprising: 
 measuring a first channel interference that the first frequency band causes to the second frequency band;    determining a frequency spreading parameter according to the first channel interference;    measuring a second channel interference that the second frequency band causes to the first frequency band;    receiving link information from the first system according to the second channel interference and determining a power allocation map according to the link information; and    transmitting and receiving data according to the frequency spreading parameter and the power allocation map.    
   
   
       2 . The method of  claim 1 , wherein the first system is authorized to use the first and second frequency bands and the second system is not authorized to use the first and second frequency bands.  
   
   
       3 . The method of  claim 1 , wherein the determination of the frequency spreading parameter further comprises calculating the Carrier-to-Interference and Noise Ratio (CINR) of each subcarrier in the second frequency band according to the first channel interference.  
   
   
       4 . The method of  claim 3 , wherein the determination of the frequency spreading parameter further comprises calculating a threshold Signal-to-Interference and Noise Ratio (SINR) for the each subcarrier using the CINR of the each subcarrier.  
   
   
       5 . The method of  claim 4 , wherein the calculation of the threshold SINR comprises defining a plurality of threshold SINRs based on a reference threshold SINR according to frequency spreading lengths.  
   
   
       6 . The method of  claim 5 , wherein the reference threshold SINR is a minimal threshold SINR required for achieving a target Bit Error Rate (BER) for data transmission and reception in the second system.  
   
   
       7 . The method of  claim 5 , wherein each of the frequency spreading lengths is a power of 2 (2 k , k=1, 2, 3, . . . , K) where K is a logarithmic function of a maximal frequency spreading length with base 2.  
   
   
       8 . The method of  claim 7 , wherein the determination of the frequency spreading parameter further comprises determining a frequency spreading length and the number of symbols spread to the frequency spreading length.  
   
   
       9 . The method of  claim 8 , wherein the determination of the number of spread symbols comprises determining the number of the spread symbols according to the number of subcarriers satisfying a threshold SINR.  
   
   
       10 . The method of  claim 1 , wherein the reception of the link information comprises requesting a link margin to the first system if the second channel interference is larger than an interference threshold of the first system and receiving the link information including the link margin from the first system.  
   
   
       11 . The method of  claim 1 , wherein the determination of the power allocation map comprises determining a power reduction value for the first frequency band with respect to a power level of the second frequency band according to the received link information.  
   
   
       12 . The method of  claim 11 , wherein the determination of the power reduction value comprises determining the power reduction value stepwise to be 1/2 m  of the power level of the second frequency band, where M is a logarithmic function of a maximal power reduction value with base 2.  
   
   
       13 . The method of  claim 11 , wherein the determination of the power allocation map further comprises determining a time spreading length according to the power reduction value for the first frequency band.  
   
   
       14 . The method of  claim 13 , wherein the time spreading length is a power of 2 (2 m , m=1, 2, 3, . . . , M), where M is a logarithmic function of a maximal power reduction value with base 2.  
   
   
       15 . The method of  claim 13 , wherein the determination of the power allocation map comprises determining the time spreading length and determining the number of subcarriers for which power is reduced for the time spreading length.  
   
   
       16 . The method of  claim 1 , wherein the data transmission and reception comprises, upon generation of data to be sent in the second frequency band, frequency-spreading the data according to the determined frequency spreading parameter and processing the frequency-spread data by time spreading and power reduction according to the power allocation map.  
   
   
       17 . The method of  claim 16 , wherein the frequency spreading comprises spreading the data to a frequency spreading length included in the frequency spreading parameter and multiplying the frequency-spread data by a spreading code.  
   
   
       18 . The method of  claim 17 , wherein the spreading of the data to the frequency spreading length comprises allocating the data repeatedly to as many subcarriers as the frequency spreading length.  
   
   
       19 . The method of  claim 17 , wherein the spreading code is an orthogonal binary Hadamard sequence.  
   
   
       20 . The method of  claim 17 , wherein the frequency spreading comprises modulating the data in a modulation scheme, converting the modulated data to parallel data, and spreading the parallel data to a frequency spreading length included in the frequency spreading parameter.  
   
   
       21 . The method of  claim 16 , wherein the time spreading and power reduction comprises repeatedly storing the frequency-spread data according to a time spreading length included in the power allocation map and the number of subcarriers for which power is reduced for the time spreading length.  
   
   
       22 . The method of  claim 21 , wherein the time spreading and power reduction further comprises reducing the power of the repeatedly stored data for the time spreading length.  
   
   
       23 . The method of  claim 22 , wherein the data transmission and reception comprises processing the power-reduced data by Inverse Fast Fourier Transform (IFFT), converting the IFFT data to serial data, adding a Cyclic Prefix (CP) to the serial data, and transmitting the CP-added data to a receiver of the second system.  
   
   
       24 . The method of  claim 1 , wherein the data transmission and reception comprises, upon receipt of data in the second frequency band, time-despreading the received data and combining the time-despread data according to the power allocation map, and frequency-despreading the combined data according to the frequency spreading parameter.  
   
   
       25 . The method of  claim 24 , wherein the time despreading and combining comprises combining the received data for a time spreading length included in the power allocation map.  
   
   
       26 . The method of  claim 25 , wherein the combining of the received data comprises combining the received data after a time equal to the time spreading length according to a power decrease from the power of the second frequency band for the time spreading length.  
   
   
       27 . The method of  claim 24 , wherein the time despreading and combining comprises removing a CP from the received data, converting the CP-removed data to parallel data, processing the parallel data by Fast Fourier transform (FFT), time-despreading the FFT data and combining the time-despread data.  
   
   
       28 . The method of  claim 24 , wherein the frequency despreading using the frequency spreading parameter comprises multiplying the time-despread and combined data by a spreading code and frequency-despreading the multiplied data to a frequency spreading length included in the frequency spreading parameter.  
   
   
       29 . The method of  claim 28 , wherein the frequency despreading comprises summing the multiplied data for the frequency spreading length and dividing the sum by the frequency spreading length.  
   
   
       30 . The method of  claim 28 , wherein the spreading code is an orthogonal binary Hadamard sequence.  
   
   
       31 . The method of  claim 28 , wherein the data transmission and reception comprises converting the frequency-despread data to serial data and demodulating the serial data in a predetermined method.  
   
   
       32 . A system for transmitting and receiving data in a communication system having a first system for providing a communication service in a first frequency band and a second system for providing a communication service in a second frequency band different from the first frequency band, the system comprising: 
 the second system for measuring a first channel interference that the first frequency band causes to the second frequency band, determining a frequency spreading parameter according to the first channel interference, measuring a second channel interference that the second frequency band causes to the first frequency band, receiving link information from the first system according to the second channel interference and determining a power allocation map according to the link information, and transmitting and receiving data according to the frequency spreading parameter and the power allocation map.    
   
   
       33 . The system of  claim 32 , wherein the first system is authorized to use the first and second frequency bands and the second system is not authorized to use the first and second frequency bands.  
   
   
       34 . The system of  claim 32 , wherein the second system calculates the Carrier-to-Interference and Noise Ratio (CINR) of each subcarrier in the second frequency band according to the first channel interference.  
   
   
       35 . The system of  claim 34 , wherein the second system calculates a threshold Signal-to-Interference and Noise Ratio (SINR) for the each subcarrier using the CINR of the each subcarrier and determines the frequency spreading parameter using the threshold SINRs.  
   
   
       36 . The system of  claim 35 , wherein the second system defines a plurality of threshold SINRs based on a reference threshold SINR according to frequency spreading lengths.  
   
   
       37 . The system of  claim 36 , wherein the reference threshold SINR is a minimal threshold SINR required for achieving a target Bit Error Rate (BER) for data transmission and reception in the second system.  
   
   
       38 . The system of  claim 36 , wherein each of the frequency spreading lengths is a power of 2 (2 k , k−1, 2, 3, . . . , K) where K is a logarithmic function of a maximal frequency spreading length with base 2.  
   
   
       39 . The system of  claim 38 , wherein the second system determines the frequency spreading parameter by determining a frequency spreading length and the number of symbols spread to the frequency spreading length.  
   
   
       40 . The system of  claim 39 , wherein the second system determines the number of the spread symbols according to the number of subcarriers satisfying a threshold SINR.  
   
   
       41 . The system of  claim 32 , wherein the second system requests a link margin to the first system if the second channel interference is larger than an interference threshold of the first system and receives the link information including the link margin from the first system.  
   
   
       42 . The system of  claim 32 , wherein the second system determines a power reduction value for the first frequency band with respect to a power level of the second frequency band according to the received link information.  
   
   
       43 . The system of  claim 42 , wherein the second system determines the power reduction value stepwise to be 1/2 m  of the power level of the second frequency band, where M is a logarithmic function of a maximal power reduction value with base 2.  
   
   
       44 . The system of  claim 42 , wherein the second system determines the power allocation map by determining a time spreading length according to the power reduction value for the first frequency band.  
   
   
       45 . The system of  claim 44 , wherein the time spreading length is a power of 2 (2 m , m=1, 2, 3, . . . , M), where M is a logarithmic function of a maximal power reduction value with base 2.  
   
   
       46 . The system of  claim 44 , wherein the second system determines the power allocation map by determining the time spreading length and the number of subcarriers for which power is reduced for the time spreading length.  
   
   
       47 . The system of  claim 32 , wherein the second system comprises a transmitter having a first spreader for, upon generation of data to be sent in the second frequency band, frequency-spreading the data according to the determined frequency spreading parameter and a second spreader for processing the frequency-spread data by time spreading and power reduction according to the power allocation map.  
   
   
       48 . The system of  claim 47 , wherein the first spreader performs the frequency spreading by spreading the data to a frequency spreading length included in the frequency spreading parameter and multiplying the frequency-spread data by a spreading code.  
   
   
       49 . The system of  claim 48 , wherein the first spreader spreads the data to the frequency spreading length by allocating the data repeatedly to as many subcarriers as the frequency spreading length.  
   
   
       50 . The system of  claim 48 , wherein the spreading code is an orthogonal binary Hadamard sequence.  
   
   
       51 . The system of  claim 48 , wherein the transmitter further comprises a modulator for modulating the data in a modulation scheme and a first converter for converting the modulated data to parallel data and providing the parallel data to the first spreader.  
   
   
       52 . The system of  claim 47 , wherein the transmitter further comprises a second spreader for repeatedly storing the frequency-spread data according to a time spreading length included in the power allocation map and the number of subcarriers for which power is reduced for the time spreading length.  
   
   
       53 . The system of  claim 52 , wherein the second spreader reduces the power of the repeatedly stored data for the time spreading length.  
   
   
       54 . The system of  claim 53 , wherein the transmitter further comprises a second converter for processing the power-reduced data by Inverse Fast Fourier Transform (IFFT), a third converter for converting the IFFT data to serial data, and a Cyclic Prefix (CP) adder for adding a CP to the serial data and transmitting the CP-added data to a receiver of the second system.  
   
   
       55 . The system of  claim 32 , wherein the second system comprises a receiver having a first despreader for, upon receipt of data in the second frequency band, time-despreading the received data and combining the time-despread data according to the power allocation map, and a second despreader for frequency-despreading the time-despread and combined data according to the frequency spreading parameter.  
   
   
       56 . The system of  claim 55 , wherein the first despreader combines the received data for a time spreading length included in the power allocation map.  
   
   
       57 . The system of  claim 56 , wherein the first despreader combines the received data after a time equal to the time spreading length according to the a power decrease from a power of the second frequency band during the time spreading length.  
   
   
       58 . The system of  claim 55 , wherein the receiver further comprises a remover for removing a CP from the received data, a first converter for converting the CP-removed data to parallel data, and a second converter for processing the parallel data by Fast Fourier transform (FFT) and providing the FFT data to the first despreader.  
   
   
       59 . The system of  claim 55 , wherein the second despreader multiplies the time-despread and combined data by a spreading code and frequency-despreads the multiplied data to a frequency spreading length included in the frequency spreading parameter.  
   
   
       60 . The system of  claim 59 , wherein the second despreader sums the multiplied data for the frequency spreading length and divides the sum by the frequency spreading length.  
   
   
       61 . The system of  claim 59 , wherein the spreading code is an orthogonal binary Hadamard sequence.  
   
   
       62 . The system of  claim 59 , wherein the receiver further comprises a third converter for converting the data despread to the frequency spreading length to serial data and a demodulator for demodulating the serial data in a demodulating method.